Semiconductor integrated circuit device

ABSTRACT

In a low power consumption mode in which prior data is retained upon power shutdown, the return speed thereof is increased. While use of an existent data retaining flip-flop may be considered, this is not preferred since it increases area overhead such as enlargement of the size of a cell. A power line for data retention for power shutdown is formed with wirings finer than a usual main power line. Preferably, power lines for a data retention circuit are considered as signal lines and wired by automatic placing and mounting. For this purpose, terminals for the power line for data retention are previously designed by providing the terminals therefore for the cell in the same manner as in the existent signal lines. Additional layout for power lines is no longer necessary for the cell, which enables a decrease in the area and design by an existent placing and routing tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/797,034, filed Apr. 30, 2007, which, in turn, is a continuation ofU.S. application Ser. No. 11/320,751, filed Dec. 30, 2005 (now U.S. Pat.No. 7,217,963), which, in turn, is a continuation of U.S. applicationSer. No. 10/921,854, filed Aug. 20, 2004 (now U.S. Pat. No. 7,023,058);the entire contents of which are incorporated herein by reference.

CLAIM FOR PRIORITY

The present application claims priority from Japanese application JP2003-384237 filed on Nov. 13, 2003, and Japanese application JP2004-185475 filed on Jun. 23, 2004, the contents of which are herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention concerns a semiconductor integrated circuit devicewhich is particularly useful when applied to system LSIs or microprocessors.

BACKGROUND OF THE INVENTION

In system LSIs used for a gizmo (personal digital assistant (PDA),hand-held device) typically represented by mobile telephones, there hasbeen an increasing demand for long time operation by a battery ofrestricted capacity. Particularly, in a mobile telephone, it isextremely important to reduce the power consumption during a longwaiting time (a state in which the power source is turned on, butprocessing under high load is not conducted) in order to satisfy therequirement for long time operation. One of the methods includesstopping all clocks of the system LSI in the standby mode (referred toas a software standby state which is called a standby mode with gatingof the system clock distribution). In the software standby state, sinceclocks in the system LSI are stopped upon entering the standby mode, theconsumption of current by the circuit operation in the system LSI isreduced to substantially zero. Accordingly, the standby current in thestandby mode consists only of the consumption of current due to leakagecurrent.

However, in a case of using an insulated gate type field effecttransistor using a modern fine process (in the present application, theinsulated gate type field effect transistor is referred to as a MISFET),various kinds of leakage current are extremely large, being typicallyrepresented by a subthreshold leakage current caused by lowering of thethreshold voltage of transistors in accordance with the voltage loweringof the power voltage or gate tunneling leakage current caused byreduction of the thickness of the gate insulation film in a MISFET.Since the standby current consumes power, a long waiting time cannot beattained.

With the situations described above, a method for effecting shut down ofthe power for the system LSI during the standby mode (referred to as theU-standby mode) has been proposed by T. Yamada, et al., “A 133 MHz 170mW 10 μA Standby Application Processor for 3G Cellular Phones”. ISSCC2002, February, pp. 370-371 (Non-Patent Document 1). In the U-standbymode, the supply of power is shut down except for circuits of a minimalnumber required for returning when it enters into the waiting state. Asa result, not only the consumption of current by the circuit operation,but also the consumption of current due to leakage current are reducedsubstantially to zero, and the standby current can be reduced tosubstantially zero.

Then, when both of them are compared in view of the returning time fromthe standby mode, they are as described below. At first, in the softwarestandby state, since the internal status of the system LSI (such as aregister value) can be retained also in the standby mode, it is possibleto return from the standby mode by interruption. Accordingly, the timerequired for returning is about equal to the time necessary forrestarting the clocks, and so it can be returned at high speed. On thecontrary, in the U-standby mode, since the internal status of the systemLSI is destroyed by the power shutdown, it cannot be returned from thestandby mode only by interruption, and so resetting is necessary for thereturn to operation. The resetting includes booting of the softwarenecessary for the initialization and operation of the system LSI andneeds a long time. Since software booting needs a number of instructionsto be conducted, the processing time is particularly long. In a the caseof returning from the U-standby mode, the interruption is not conductedfor the interruption request as it is, but resetting is first appliedand then processing corresponding to the interruption request isconducted after booting of the software.

Further, as disclosed in S. Mutoh, et al., “A 1V Multi-Threshold VoltageCMOS DSP with an Efficient Power Management Technique for Mobile PhoneApplication, ISSCC 1996, February, pp. 168-169 (Non-Patent Document 2),and V. Zyuban, et al., “Low Power Integrates Scan-Retention Mechanism”,ISLPED 2002, August, pp. 98-102 (Non-Patent Document 3), it has beenproposed to supply power to a portion of the data retention circuits inthe circuit block under power shutdown in the standby mode to retain thedata also in the standby mode. Specifically, a latch circuit suppliedwith power even in a standby mode is disposed to the flip-flop in thecircuit block and it operates to retain the internal data also duringpower shutdown by the latch circuit, thereby enabling a return to theoriginal state at high speed.

SUMMARY OF THE INVENTION

The present inventors have studied the data retention circuits asdescribed above and have found that they involve the followingconsiderations. FIG. 2 shows the circuit arrangement of a flip-flop withdata retention in a power down mode as disclosed in Non-Patent Document3. This circuit has a constitution in which power for the main latchpart (master latch) is shut down during the standby mode, and data isretained during the standby mode by the sub-latch part (scan/retentionlatch) which is usually supplied with power. The power supply for themain latch part and combinational circuits connected therewith isconnected by way of a power switch to an unillustrated virtual powerline, and it shows the necessity for a virtual power line directlyconnected with the main latch part and combinational circuits connectedtherewith in addition to the power line (VDD, GND). Accordingly, it hasbeen found that for the layout of the circuit constitution shown in FIG.3, at least three power lines, i.e., VDD, VSS, and a virtual power lineare necessary (in a case of providing a power switch on one side of VDDor VSS), and at least three power lines have to be laid out for onecell.

This is attributable to the fact that a general system LSI is laid outby arranging standard cells (hereinafter simply referred to as cells) byautomatic placing and routing using CAD. FIG. 3 is a view showing alayout for an integrated circuit constituted by placing the cells.However, only the cells and the main power lines are illustrated, withsignal wirings, etc. being omitted. The cells are represented byrectangles 301 and 302. Each cell is mounted with circuits for attainingbasic logic, such inverters, NANDs or the like. A desired logic circuitis obtained by laying out the cells and wiring them to each other. Whilethe scale of the circuits is different depending on the basic logicattained by the cells, it is typical to align the cell height (directiony) and vary the cell width (direction x) in accordance with the circuit.This is attributable to conducting the layout for main power lines in amesh-like form. That is, since power lines 303 a to 303 g extending inthe direction x are placed in the first metal layer substantially at anequal distance relative to each other to supply power necessary forcircuit operation, the layout for the main power lines and the layoutfor the cells are aligned.

Under the design environment for the layout, even when only a portion ofthe cells require wirings both for the power line and the virtual powerline (flip-flop), such power lines and virtual power lines have to bewired also for other cells not requiring data retention during powershutdown (for example, an inverter, NAND circuit, etc.). Accordingly, ifa power line identical with the virtual power line is further laid outrelative to the first metal layer, the cell height will be increased andthe effect on the entire layout is no longer negligible. On the otherhand, if it is intended to further layout the main power line whilefixing the height of the cell as it is by utilizing the wiring channelfor signal lines, there may be a worry that the degree of freedom forthe signal line is extremely restricted.

As described above, no consideration has been given to the layout forretaining data in flip-flop cells that are distributed and placed asdescribed above also during power shutdown and for suppressing theoverhead of the circuit area under the existent design environment forlayout.

In accordance with the present invention, notice has been taken of thefact on that the data retention circuit for retaining data during powershutdown requires no such large current supply performance as requiredfor normal operation, and it has been determined to supply an operationvoltage by a power line that is smaller in size than the usual mainpower line. Preferably, the power line for the data retention circuit isconsidered as a signal line and is wired upon placing and routing byusing CAD. This is adaptable for the CAD-assisted design environment fora layout. In this case, the power terminals for the data retentioncircuit are previously disposed to the cell in the same manner as forthe usual signal line terminals. This no longer requires an additionallayout for the power lines in the cell to enable area saving and, inaddition, design by existent placing and routing tools is enabled.

The returning time from the power shutdown can be shortened drastically,and, therefor, the overhead to the circuit area can be decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of a layout for power lines inaccordance with the present invention;

FIG. 2 is a schematic diagram which shows an example of a flip-flop fordata retention;

FIG. 3 is a diagram which shows an example of a semiconductor integratedcircuit formed by laying out standard cells;

FIG. 4 is a diagram showing another example of a layout for power linesin accordance with the present invention;

FIG. 5 is a diagram showing a further example of a layout for powerlines in accordance with the present invention;

FIG. 6 is a schematic circuit diagram showing wirings in which theinvention is applied to a case of power shutdown on the ground side;

FIG. 7A is a schematic circuit diagram showing wirings in which theinvention is applied to a case of power shutdown on the high voltageside;

FIG. 7B is a schematic diagram which shows an example of a circuitconstituting a power switch SW1 by a voltage regulator;

FIG. 8 is a schematic circuit diagram showing wirings in which theinvention is applied to a case of power shutdown both on the ground sideand the high voltage side;

FIG. 9A is a diagram showing the symbols for the cell of a nonvolatileflip-flop in accordance with the invention;

FIG. 9B is a diagram showing the symbols for the cell of a nonvolatileflip-flop in accordance with the invention;

FIG. 9C is a diagram showing the symbols for the cell of a nonvolatileflip-flop in accordance with the invention;

FIG. 9D is a diagram showing the symbols for the cell of a nonvolatileflip-flop in accordance with the invention;

FIG. 10 is a schematic circuit diagram showing an example of amaster-slave latch;

FIG. 11 is a schematic circuit diagram showing a nonvolatile flip-flop(master-slave latch) in accordance with the invention;

FIG. 12 is an operation waveform chart of the circuit shown in FIG. 11;

FIG. 13 is a schematic circuit diagram showing another example of anonvolatile flip-flop (master-slave latch) in accordance with theinvention;

FIG. 14 is an operation waveform chart of the circuit shown in FIG. 13;

FIG. 15 is a schematic circuit diagram which shows a nonvolatileflip-flop (master-slave latch with scan function) in accordance with theinvention;

FIG. 16 is an operation waveform chart of the circuit shown in FIG. 15;

FIG. 17 is a schematic circuit diagram showing an example of a pulselatch;

FIG. 18A is a schematic circuit diagram which shows a nonvolatileflip-flop (pulse latch) in accordance with the invention;

FIG. 18B is a schematic circuit diagram which shows a nonvolatileflip-flop (pulse latch) in accordance with the invention;

FIG. 19 is an operation waveform chart of the circuit shown in FIG. 18A;

FIG. 20 is a schematic circuit diagram which shows a modified embodimentin a case of providing the scan function to the circuit in FIG. 18A orFIG. 18B;

FIG. 21 is a schematic circuit diagram which shows another example of anonvolatile flip-flop (sense-amplifier based flip-flop) in accordancewith the invention;

FIG. 22 is an operation waveform chart of the circuit shown in FIG. 21;

FIG. 23A is a diagram showing power connection control for a dataretention storage element circuit of a nonvolatile flip-flop;

FIG. 23B is a diagram showing power connection control for a dataretention storage element circuit of a nonvolatile flip-flop;

FIG. 24 is a schematic circuit diagram which shows a modified example ofa pulse generator of the pulse latch shown in FIG. 18A and FIG. 18B;

FIG. 25A is a schematic circuit diagram showing an example of the methodof generation of a power line signal for data retention VSS_SIG;

FIG. 25B is a schematic circuit diagram showing an example of the methodof generation of a power line signal for data retention VSS_SIG;

FIG. 25C is a schematic circuit diagram showing an example of the methodof generation of a power line signal for data retention VSS_SIG;

FIG. 26 is an operation waveform chart showing a case where the controlmethod for generation of a power line signal for data retention VSS_SIGin FIG. 25 is applied to the nonvolatile flip-flop shown in FIG. 11;

FIG. 27 is a schematic circuit diagram showing a circuit constitutingthe nonvolatile flip-flop in FIG. 11 by using plural kinds of MISFET;

FIG. 28A is a schematic circuit diagram showing a modified embodiment ofa nonvolatile flip-flop for improving the noise immunity;

FIG. 28B is a schematic circuit diagram showing a modified embodiment ofa nonvolatile flip-flop for improving the noise immunity;

FIG. 28C is a schematic circuit diagram showing a modified embodiment ofa nonvolatile flip-flop for improving the noise immunity;

FIG. 28D is a schematic circuit diagram showing a modified embodiment ofa nonvolatile flip-flop for improving the noise immunity;

FIG. 29 is a diagram which shows an example of element layout for anonvolatile flip-flop in accordance with the invention;

FIG. 30A is a cross sectional view of a normal inverter as shown in FIG.29;

FIG. 30B is a cross sectional view of a normal inverter as shown in FIG.29;

FIG. 31A is a cross sectional view of a nonvolatile inverter as shown inFIG. 29;

FIG. 31B is a cross sectional view of a nonvolatile inverter as shown inFIG. 29;

FIG. 32 is a layout diagram for a first region AE1;

FIG. 33 is a diagram showing the chip constitution of an integratedcircuit using the invention;

FIG. 34 is a comparison table for low current consumption modes;

FIG. 35 is a diagram showing transition of state between types of modes;

FIG. 36 is a block diagram showing an example of a control circuit inthe standby mode STBYC;

FIG. 37 is a timing chart for a transition sequence transiting from anormal operation mode to a second standby mode;

FIG. 38 is a timing chart for a return sequence returning from thesecond standby mode to the normal operation mode;

FIG. 39 is a schematic circuit diagram which shows a nonvolatileflip-flop (master-slave latch) in accordance with the invention;

FIG. 40 is an operation waveform chart of the circuit shown in FIG. 39;

FIG. 41 is a schematic circuit diagram which shows a nonvolatileflip-flop (master-slave latch) in accordance with the invention; and

FIG. 42 is an operation waveform chart of the circuit shown in FIG. 41.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an embodiment of a layout image of chip wirings inaccordance with the present invention. The drawing shows an example inwhich usual main power lines, that is, power lines VDD (for example, at1.2 V) and virtual power lines VSSM (0 V), and a power line for dataretention VSS_SIG (0 V) for a nonvolatile flip-flop NVFF (hereinafterreferred to nonvolatile FF) are wired. In this example, since it isassumed that the power line on the ground side (low potential side) isplaced under shut down control during a standby mode, the power line onthe low potential side constitutes the virtual power line VSSM. In theplacing and routing tool, the virtual power line VSSM is considered as asubstantial ground line of the cells. As illustrated in the drawing, thepower line VSS_SIG is connected with terminals of the nonvolatile FFNVFF dispersed in a circuit block by the placing and routing tool byusing CAD by way of an optional route and by using optional wiringlayers.

By wiring the power line VSS_SIG as described above, since a layout canbe produced by placing and routing by using CAD while replacing existentflip-flop cells with nonvolatile FF cells without changing the layoutdimension of each of the functional circuits (cells), such as invertercircuits or NAND circuits, the design can be facilitated.

Now, the wiring widths in a predetermined wiring layer (first metallayer M1 in the drawing) will be compared. Assuming that the wiringwidth for the main power line is W1, the wiring width for the power linefor data retention VSS_SIG is W2, and the wiring width for a signal linenot illustrated (wiring connected with the input/output terminal of thecell) is W3, a relation: W1>W2=W3 is established. Taking the processscattering for the wiring width into consideration, a relation:(W1−W2)>(W3−W2) is established.

FIG. 4 and FIG. 5 show other examples of the wiring layout. The degreeof freedom of the wire connection in this example is less than that ofthe example in FIG. 1, but it has an advantage in that layout can becarried out simply in a case where the wiring channel has a margin. Ithas a feature in the layout of suppressing the area overhead byadditional wirings by decreasing the wiring width for the power line fordata retention VSS_SIG to less than that of the main power line, whiletaking notice of the fact that the current supply performance of thepower line for data retention VSS_SIG may be smaller than that of themain power line. In FIG. 4, the power line for data retention VSS_SIG,having a narrower wiring width compared with that of the main powerline, is arranged in parallel in a layer identical with the main powerline. This sometimes requires increasing the height of the cell. On theother hand, in FIG. 5, the power line for data retention VSS_SIG of anarrower wiring width compared with that of the main power line, isarranged in the layer below the main power line M1 (for example, metal 0layer M0). This may save the consumption of the wiring channel and needsno increase for the cell height. Accordingly, the layout in FIG. 5 canbe more compact than the layout in FIG. 4. However, since the materialfor the metal is often different in layer M0 generally, the resistanceof the wiring may possibly be increased. The wiring form of the typeshown in FIG. 5 is the result of a known wiring method in a so-calledsubstrate bias control of controlling the substrate electrode for thecircuit independently of the power line. Also, in this case, assumingthe wiring width of the main power line is W1, the wiring width for thepower line for data retention VSS_SIG is W2, and the wiring width of thenot illustrated signal line is W3, a relation: (W1−W2)>(W3−W3) isestablished.

The reason why the power line for data retention of a nonvolatile FFNVFF can be wired by a method different from that of the existent mainpower line will be described more specifically. Generally, it isnecessary that the resistance of the main power line should be loweredin order to maintain the speed of a MISFET constituting a functionalblock. For this purpose, the main power lines are wired in a mesh, asshown in FIG. 3. However, since it may suffice that the power suppliedduring the power shutdown state of the nonvolatile FF NVFF may be suchthat the leakage current during the standby mode can be supplied, anincrease in the resistance of the wiring gives no significant problem.For example, assuming that the size of a MISFET necessary for retainingdata of one nonvolatile FF NVFF during standby mode is 1 μm by the gatewidth and that the gate voltage for flowing 1 nA per unit width (1 μm)at a normal temperature (25° C.) of constituting MISFET is 0.15 V, theleakage current during the standby mode per one nonvolatile FF NVFF isabout 30 pA. Assuming that the rate of the flip-flops in a chip is about4000 N/mm² and considering a chip of 7 mm×7 mm in size, the total numberof the all nonvolatile FF NVFF is 196,000, and the leakage current isabout 6 pA. Even when it is assumed that the number is larger by afactor of 1.5 considering the scattering in the manufacture (thresholdvalue variation: 100 mV) and high temperature (45° C.), the leakagecurrent is about 180 μA. Since the current only at such a level isnecessary, the power line for data retention during power shutdown for anonvolatile FF NVFF does not need the use of a general main power linestructure.

However, at a high temperature, such as 80° C., since the DC currentincreases, there may be a worry of electro-migration for fine wirings.Also, in such a case, since the current necessary for individual cellsis still small, this can be coped with by enlargement of the wiringwidth for wiring at the base for branching on the side of the controlledcircuit in the standby mode STBYC through which a great amount ofcurrent flows, or by increasing the number of through holes at theportion. In the layout shown in FIG. 5, it can be coped with byincreasing the width of the power line existing in the longitudinaldirection.

Now, connection between each of the circuit elements will be described.FIG. 6 shows an example of power shut-down from the ground side duringthe standby mode corresponding to the layout in FIG. 1, and this is acircuit diagram also including the control system therefor. It shows afunctional block AE1 put under power shut-down control during thestandby mode, a power switching circuit SW1 for controlling the powersupply to the function block AE1 and a control circuit in standby modeSTBYC for controlling the nonvolatile FF NVFF and the power switchingcircuit SW1 of the function block AE1. As will be described later inconjunction with FIG. 32, a central processing unit CPU (hereinafterreferred to simply as a CPU), a digital signal processor (hereinafterreferred to simply as a DSP) and embedded circuit modules, such as anMPEG accelerator, are integrated, for example, in the function blockAE1. Power is normally supplied to the control circuit in the standbymode STBYC, and the power is supplied continuously unless the power isshut down from the outside of the chip. The function block AE1 has afeature in that logic circuits are integrated and the nonvolatile FFNVFF of the invention is used for the flip-flop thereof. In a case wherethe function block AE1 is placed under power shut-down control, thecontrol circuit in the standby mode STBYC conducts shutdown control forthe power switching circuit SW1 by a control signal SW1-C and controlsthe nonvolatile FF NVFF by an NVFF control signal group NVCTL. Further,the power line for data retention VSS_SIG during power shut-down for thenonvolatile FF NVFF is also supplied with power from the control circuitin the standby mode STBYC and is connected by way of an optional routeto the nonvolatile FF NVFF in the function block AE1. The connection maybe in the form of a daisy chain, or it may be connected in a tree type.It may also be wired freely using a placing and routing method byplacing and routing using CAD. In FIG. 6, the circuit is drawn such thatthe power line for data retention VSS_SIG is connected from one terminalof the control circuit in, standby mode STBYC to all of the nonvolatileFF NVFF, but it may be connected from two or more of the terminals ofthe control circuit in the standby mode STBYC to the nonvolatile FFNVFF. Such a constitution can decrease the number of nonvolatile FF NVFFconnected per one terminal of the control circuit in the standby modeSTBYC, to provide the advantage of lowering the current supplyperformance required for the power line for data retention VSS_SIG.However, since it is necessary to previously group the nonvolatile FFNVFF on every terminal in a case of wiring using a placing and routingtool, this complicates the layout step.

FIG. 7A shows another example of the connection between each of thecircuit elements. In this case, the function block AE1 is power-shutdownon the high potential side (VDD) by the power switching circuit SW1, andcontrol is conducted by a control signal SW1-C from the control circuitin the standby mode STBYC. The NVFF control signal group NVSTL and thepower line for data retention VSS_SIG are identical with those in FIG.6. The constitution of FIG. 7A is effective in a case where the functionblock AE1 supplies internal power while regulating the external power.The power switching circuit SW1 may be replaced with a regulator. FIG.7B shows an example of such a constitution. The circuit is disclosed in“Super LSI Memory” written by Kiyoo Ito, in page 271, published fromBaifukan (first print issued in 1994).

FIG. 8 shows a further example of the connections between each of thecircuit elements. Power shut-down to the function block AE1 is conductedby shutting down both the high potential side power line for dataretention VDD and the low potential side power line for data retentionVSS by the power switching circuit SW1. The control is conducted by thecontrol signal SW1-C from the control circuit in the standby mode STBYC.This example has a feature in that it requires two types of power linefor data retention, that is, a power line for data retention VDD_SIG onthe high potential side and a power line for data retention VSS_SIG onthe low potential side.

As described above, the invention is applicable for shutting down on anyof the low potential side and the high potential side. An example ofshutting down the power on the low potential side will be described.That is, unless otherwise specified, a global grounded power supplied toeach of the cells in the chip is provided by a virtual power line VSSMby way of the N-type MISFET for power switching from a real groundedVSS, and the ground power supplied to the nonvolatile part is providedby a power line VSS_SIG. While there is no particular restriction, thepower shutdown N-type MISFET is constituted with a MISFET having a largegate dielectric film thickness and a high threshold voltage, forexample, an I/O circuit, etc. The subthreshold leakage current flowingthrough the circuit in the standby mode can be decreased effectively byusing this type of N-type MISFET, which has large threshold voltage, anda so-called gate tunneling leakage current flowing through the circuitcan also be reduced effectively by means of the thick gate dielectricfilm. In this case, the control signal SW1-C has an amplitude inaccordance with a high voltage for an I/O, for example (3.3 V).

As one of the features, the invention has a mechanism of retaining theinternal data for a CPU and embedded circuit modules by a nonvolatile FFNVFF present in the modules, and, desirably, it adopts a design methodof wiring the power line for data retention to the nonvolatile FF NVFFas a signal line. The difference between the signal power line used forthe nonvolatile FF NVFF and a general main power line in view of theapparatus is that, since the signal power line is connected ad hoc inthe design stage of placing and routing the cells, the wiring does nothave a neat geometrical pattern and takes a random connection, as shownin FIG. 1. It has an advantageous effect of increasing the degree ofdesign freedom due to free wiring by the placing and routing tool, andso it is capable of providing an efficient layout.

FIGS. 9A to 9D are views showing symbols for the nonvolatile FF cell(NVFF cell) used in the placing and routing tool. FIG. 9A shows anexample of using only one signal line RSTR as a data retention controlsignal group NVCTL of a nonvolatile FF NVFF. The NVFF cell compriseseach of input pins for D (data input pin), CLK (clock pin), RSTR(nonvolatile FF control pin), and VSS_SIG (signal power input pin) andoutput pins for Q (data output pin).

On the other hand, FIG. 9B shows an example of using two signals linesRSTR and RESTRb as a data retention control signal group NVCTL of thenonvolatile FF NVFF. The NVFF cell comprises each of input pins for D(data input pin), CLK (clock pin), RSTR and RSTRb (nonvolatile FFcontrol pin) and VSS_SIG (signal power line input pin) and output pinsfor Q (data output pin).

FIG. 9C shows an example of a nonvolatile FF with a scan function in acase of using only one signal line RSTR as a data retention controlsignal group NVCTL thereof. The NVFF cell has a feature of comprisingeach of inputs for D (data input pin), SI (scan data input pin), SE(scan enable pin), CLK (clock pin), RSTR (nonvolatile FF control pin),VSS_SIG (signal power input pin), and each of output pins for Q (dataoutput pin) and SO (scan data output pin).

FIG. 9D also shows an example of a nonvolatile FF with a scan function,in a case of using two signal lines RSTR and RSTRb as the data retentioncontrol signal group NVCTL. The NVFF cell has a feature of comprisingeach of inputs for D (data input pin), SI (scan data input pin), SE(scan enable pin), CLK (clock pin), RSTR and RSTRb (nonvolatile FFcontrol pins) and VSS_SIG (signal power input pin), and each of outputpins for Q (data output pin), and SO (scan data output pin).

The cell symbols illustrated here are only examples, and the cells maybe constituted such that the group of output signal lines outputinverted signals.

Now, a concrete example of the nonvolatile FF will be described. FIG. 10shows a master-slave latch (flip-flop circuit) not having a dataretention function upon power shutdown. Combinational circuits areconnected before and after the master-slave latch to constitute asynchronous circuit.

In the circuit shown in FIG. 10, a transmission gate TG1 of the masterlatch is closed to latch data upon the rising edge of a clock (CLK:L→H), while a transmission gate TG2 of the slave latch opens to outputthe data taken in the master latch to the output Q. On the other hand,at the falling edge of the clock (CLK: H→L), the transmission gate TG1of the master latch opens while the transmission gate TG2 of the slavelatch is closed to retain the data in the slave latch.

FIG. 11 shows an example of a nonvolatile master-slave latch inaccordance with the invention. It is different from the master-slavelatch shown in FIG. 10 in that it additionally provides a control signalRSTR, a non-volatile circuit NVC, control MOS (MP1, MN1) for the slavelatch, a clocked inverter C1NV1 in the connection interface for the NVCand a slave latch (constituted with MP4, MP5, MN4, and MN5), a selector(MP2, MP3, MN2, MN3) for writing back NVC data to the slave latch, andVSS_SIG as a power source to circuits necessary upon power shutdown,such the as NVC.

FIG. 12 is an operation waveform chart showing the operation and acontrol method of the nonvolatile master-slave latch shown in FIG. 11.

Time T1 shows a clock rising state during normal operation. At the levelof the control signal RSTR=LO, since the transistors MP2 and MN2 areturned OFF and the transistors MP1 and MN1 are turned ON in FIG. 11, thefunction of a slave latch is logically identical with that of thecircuit in FIG. 10. Therefore, the input data is outputted to output Qin accordance with the rising of the clock CLK. In this case, since theclocked inverter CINV1 inserted between the node ND0 and the node NVb inthe nonvolatile circuit NVC is open, the level at the node ND0 istransferred to the nonvolatile circuit NVC and the data is written intothe node NV. In this stage, however, since MP6 and MN6 in FIG. 11 areOFF, the loop which is connecting NV and NVb for the nonvolatile circuitNVC is opened.

Now, the operation of the data storing to the nonvolatile circuit NVC ofthe nonvolatile FF NVFF in the power shut-down mode will be described.At time T2, the control signal RSTR is at first turned to the level HI.In this case, the loop of the nonvolatile circuit NVC is closed by theturning ON of the transistors MP6 and MN6. At the same time, the clockedinverter CINV1 is shut down by the turning OFF of the transistors MP4and MN4, by which the route from the slave latch to the nonvolatilecircuit NVC is disconnected. In this case, the transistors MP1 and MN1are turned OFF, while the transistors MP2 and MN2 are turned ON, bywhich the level at the NVb is fed back from the nonvolatile circuit NVCinstead of the level at the node ND1 in the slave latch. Since thetransmission gate TG2 in the master latch is closed, if the input valueat the input node D becomes the intermediate level, there is no currentflow in the powered circuit, generally.

Then, power shutdown control is conducted at T3. It is assumed here thatthe power on the ground side is shut down by the N-type MISFET. ThePSWGATE signal, which corresponds to the control signal SW1-C, controlspower switching by asserting LO. In a case of a using thick-gate-oxideMISFET which often is used in I/O circuitry, for example, the voltageamplitude of the PSWGATE is the same as that of the I/O circuit (forexample, 3.3 V). By such control, the virtual power line VSSM is shutdown from the actual ground and the potential of the virtual power lineVSSM is caused to rise toward a high potential side (VDD) by the leakagecurrent of the internal circuit. While the example of FIG. 12 shows justan intermediate level between VDD and 0 V, it actually rises to a levelinfinitely nearer to VDD due to conditions such as the scale of thecircuits to be integrated, the temperature and the MISFET thresholdvoltage. Accordingly, the usual circuit can no longer retain the data.

The time interval between the times T3 and T2 has to be decided bytaking into account the time which the whole data of the nonvolatile FFsin the chip evacuate their own NVC. Therefore, a method may beconsidered, for example, of using a driver having a small drivingcapability for driving the RSTR signal line, measuring the time untilthe driver output level exceeds a certain threshold value and startingpower shut-down control after waiting for a period several times as longas the measured time.

When power shut-down control is conducted, the potential for the virtualpower line VSSM increases and other retained data than in thenonvolatile circuit NVC disappears. Also, in this case, since the powerfor the nonvolatile circuit NVC and the inverter INV1 inputted with thecontrol signal RSTR is supplied by the power line for data retentionVSS_SIG, the internal node NV of the nonvolatile circuit NVC can retaina desired value.

On the other hand, in the power-on control, the PSWGATE signal is drivento the level HI at time T4. Then, the potential on the virtual powerline VSSM is gradually driven to 0 V and the master-slave latch is putinto a state capable of retaining data. The data from the nonvolatilecircuit NVC is at first written back by way of the transistors MP3 andMN3 to the slave latch. Since the control signal RSTR is HI level (VDD)and the inversion signal thereof is also kept at Lo level (0 V) by INV1,the data of the nonvolatile circuit NVC is undisturbed during theoperation of the master-slave latch in the power-on sequence. In thestandby mode, since the power for the driving circuit of the clocksignal CLK is also shut down, the LO level of the clock CLK cannot bekept exactly at the ground level (0 V). However, it is no problem thatthe clock signal is controlled such that the level LO is rapidlyoutputted after the application of power.

After complete the turning ON of the power switch, the control signalRSTR is dropped to LO at time T6 after confirming that the potential forthe vertical ground line VSSM has been dropped to 0 V. Thus, thetransistors MP2 and MN2 in FIG. 11 are turned OFF, and, therefore, thefeedback loop from the nonvolatile circuit NVC is opened. At the sametime the transistors MP1 and MN1 are turned ON to establish a feedbackloop from the node ND1. Further, the transistors MP4 and MN4 are turnedON to form a signal path from the slave latch to the nonvolatile circuitNVC, and the transistors MP6 and MN6 are turned OFF to open the loop ofthe latch in the nonvolatile circuit NVC. Thus, the nonvolatilemaster-slave latch in FIG. 11 can perform the normal function in theusual operation. That is, the normal operation of the master-slave latchof capturing data at the rising edge of the clock as shown at time T7,T8 is attained.

With the constitution described above, a data retention mechanism in thepower shutdown state is provided without substantial degradation of thecharacteristics of the conventional master-slave latch. Therefore, dataretention in the power shutdown state can be obtained easily and atreduced cost in case of applying this nonvolatile master-slave latch toa system LSI.

In FIG. 11, the control signal RSTR generates an inverted signal by wayof the inverter INV1 at the inside of the nonvolatile FF NVFF. This isbecause the OFF operation of the clocked inverter and the latchformation of the nonvolatile circuit NVC cannot be conducted effectivelyin a case where a large difference is present for the arrival timebetween the RSTR signal and the inverted signal thereof, with the resultthat this causes destruction of data. As in this constitution, in a casewhere the inverted signal for the RSTR signal is generated in thenonvolatile FF NVFF, therefore, the difference of the arrival timebetween these two signals can be minimized, and the problem describedabove is overcome. Further, since the number of the pins is smallercompared with the constitution in which both the control signal RSTR andits inverted signal are received, it also provides the effect ofdecreasing the number of wirings for routing, thereby facilitating thewiring.

FIG. 13 shows an example of controlling the nonvolatile control signalNVCTL by using the two signals RSTR and RSTRb which are complementary toeach other. This is different from FIG. 11 in that two clocked invertersCINV2 and CINV3 are provided, and in that the nonvolatile circuit NVC isconstituted with inverters having switches in the form of transistorsMN9 and MN10. In the drawing, MISFETs as for power shutdown of theclocked inverters CINV2 and CINV3 are designed to be providedindependently by transistors MN7, MN8, MP7, and MP8, but they may beused in common for two clocked inverters. In the same manner,transistors MN9 and MN10, operating as the power switch for thenonvolatile circuit NVC, may also be used in common between both ofthem. This provides a benefit of further saving the area.

FIG. 14 is an operation waveform chart showing the operation and thecontrol method of the nonvolatile master-slave latch shown in FIG. 13.At time T1, since the control signal RSTR=LO, this shows a rising edgeof the clock during normal operation. This is because transistors MP2and MN2 are OFF and the transistors MP1 and MN1 are ON (shown in FIG.13) when the control signal RSTR=LO (accordingly, control signalRSTRb=HI). This situation, which is the same as that described above toillustrate FIG. 12, provides a logically identical function with that ofthe master-slave latch shown in FIG. 10. Corresponding to the risingedge of the clock signal CLK, the input data D is outputted to theoutput Q. In this stage, in the example of this constitution, since theclocked inverters CINV2 and CINV3 inserted between the node ND0 and thenode NV in the nonvolatile circuit NVC are open, the data is transferredto the node NV in the nonvolatile circuit NVC. However, in this stage,since the transistors MP9 and MN10 in FIG. 13 are OFF, the loop of thenonvolatile circuit NVC is not closed.

Now, the operation of storing the data by the nonvolatile circuit NVC inthe nonvolatile FF NVFF when the power shut down is conducted will bedescribed. At time T2, the RSTR signal is at first put to the level HI.In this case, the loop of the nonvolatile circuit NVC shown in FIG. 13is closed by the turning ON of the transistors MP9 and MN10, and thepath of the clocked inverters CINV2 and CINV3 between the slave latchand the nonvolatile circuit NVC to the ground level is shut down by theturning OFF of transistors MN7 and MN8. In this case, since thetransistor MN2 is turned ON and the transistor MP1 is turned OFF, thepath of the slave latch to the high potential side power line in theusual operation is disconnected, and the current path of the driver MN3for feedback on the ground side of MN3 is formed such that feedback fromthe nonvolatile circuit NVC can be inputted. Then, when the RSTRb signalis put to the level LO at time T2′, switching MISFETs MP7 and MP8 on thehigh potential side power line for the clocked inverters CINV2 and CINV3are shut down to isolate the slave latch and the nonvolatile circuitNVC. At the same time, the transistor MP2 is turned ON and thetransistor MN1 is turned OFF, by which the feedback loop for the slavelatch in the normal operation is opened and the feedback loop from thenonvolatile circuit NVC is completely closed. Thus, even when each nodeof the slave latch takes any value during normal operation, this has noeffect on the nonvolatile circuit NVC. Since the transmission gate TG2of the master latch is closed in this case, there is no effect when thedefined value for the input D may be changed. Further, it is necessaryfor the time interval between T2 and T2′ that it allows the RSTR signalto reach the level HI in the entire chip. This can be attained by usinga driver of small driving capability as the driver for driving the RSTRsignal, measuring the time until the output of the driver reaches apredetermined threshold value or higher, and putting the RSTRb signal tothe level LO after a period several times as long as the measured time.This is because the wiring route is generally different between the RSTRsignal and the RSTRb signal, and the difference of delay between thesetwo signals cannot be assured on the premise of using the placing androuting tool. In a case where each of the RSTR signal and the RSTRbsignal reaches an identical cell at an identical delay, that is, wherewirings can be conducted in a substantially equal path, the intervalbetween times T2 and T2′ may also be controlled depending on the levelof the RSTR signal returned to the control circuit in standby mode STBYCby providing a route for turning the RSTR signal from a predeterminedposition of the RSTR signal line to the control circuit in standby modeSTBYC.

Then, power shut-down control is conducted at time T3 like that in FIG.12. A case of shut-down for the ground power line by the N-type MISFETis assumed. For this purpose, control for putting the control signalPSWGATE (SW1-C) of the N-type MISFET to the level LO is conducted.

When power shutdown control is conducted, the potential of the virtualpower line VSSM increases and retention data other than in thenonvolatile circuit NVC is eliminated. Since the power for thenonvolatile circuit NVC is supplied by the power line for data retentionVSS_SIG, the internal node NV of the nonvolatile circuit NVC continuesto hold a valid value.

On the other hand, in case of a power-on sequence, the PSWGATE signal isdriven to the level HI at time T4. Then, the level of the virtual powerline VSSM is gradually driven to 0V and the master-slave latch can holddata. The data from the nonvolatile circuit NVC is written back to theslave latch by way of MP3 and MN3. Since the RSTR signal is at HI level(VDD) and the RSTRb signal is also at Lo level (0 V), the data of thenonvolatile circuit NVC is undisturbed during the operation of themaster-slave latch in the power-on sequence. Also, in this case, asdescribed with reference to FIG. 12, since the power for the drivingcircuit of the clock signal CLK is also shut down, the LO level of theclock CLK cannot be kept exactly at the ground level (0 V). However, itis no problem that the clock signal is controlled such that the level LOis rapidly outputted after the application of power.

Then, after confirming that the power switch has been turned completelyto ON and the potential of the virtual power line VSSM is put to 0 V,the RSTR signal is put to LO at time T6. Thus, the transistor MN2 inFIG. 13 is turned OFF, the current path on the ground side of thefeedback loop from the nonvolatile circuit NVC is shut down, and thetransistor MP1 is turned ON to form a high potential side current pathfor the feedback loop of the slave latch in a normal operation. At thesame time, the transistors MP7 and MP8 are turned ON to form a highpotential side current path in the signal loop from the slave latch tothe nonvolatile circuit NVC, and the transistors MN9 and MN10 are turnedOFF, by which the loop for the latch in the nonvolatile circuit NVC isopened.

Then, when the RSTRb signal is put to the level HI at the time T6′,switching transistors MN7 and MN8 on the low potential side of theclocked inverters CINV2 and CINV3 are turned ON to connect the slavelatch with the nonvolatile circuit NVC, the transistor MP2 is turnedOFF, and the transistor MN1 is turned ON to completely close thefeedback loop of the slave latch and open the feedback loop from thenonvolatile circuit NVC. Subsequently, the invented nonvolatilemaster-slave latch works as a normal Master-Slave latch.

Further, it is necessary that the time interval between the times T6 andT6′ is long enough to allow the RSTR signal transmitted to the entirechip to reach the level LO. To realize this control, there is onemethod, for example, of using a driver having a small driving capabilityto drive the RSTR signal to LO, measuring the period until the driveroutput decreases to a certain threshold level or lower, and putting theRSTRb signal to the level HI after the period several times as long asthe measured time.

FIG. 15 shows an example of a nonvolatile master-slave circuitadditionally provided with a scan function. This is different from theconstitution shown in FIG. 11 in that a scan input signal (S1), a scanenable signal (SE) and a scan output signal (SO) are added as terminals,and in that a selector circuit SEL, and an NOR circuit in communicationwith the scan output terminal SO and an inverter are provided. Theselector circuit SEL corresponds to the inverter in communication withthe input D in FIG. 11, and this is constituted as a clocked inverter,for which degradation of the speed may substantially be taken out ofconsideration so long as the width is properly designed. The selectorcircuit SEL selects either the data input signal D or the scan inputsignal SI by the SE signal and inputs the same to the latch. In a casewhere the SE signal is at the level HI, the scan input signal SI isselected, whereas the data input signal D is selected in a case wherethe SE signal is at the level LO.

At the rising edge of the clock signal CLK (CLK: L→H), the transmissiongate TG1 of the master latch is closed to latch the data and thetransmission gate TG2 of the slave latch is opened to output the datataken into the master latch to the output Q. On the other hand, at thefalling edge of the clock signal CLK (CLK: H→L), the transmission gateTG1 of the master latch is opened and the transmission gate TG2 of theslave latch is closed to retain the data in the slave latch. In theseries of clock operations, the scan output signal SO changes insynchronization with the clock signal depending on the value of the scaninput signal SI where the SE signal is at HI, whereas it always outputsLO even when the value for the data input signal takes any value wherethe SE signal is at LO. Further, the basic operation is identical withthat in FIG. 12 and quite the same operation is attained so long as theSE signal is at LO.

Further, when the data taking route to the nonvolatile circuit NVC ischanged from the node ND0 to the node ND2, the load on the DQ pass canbe reduced to provide an effect of increasing the speed. In this case,as shown in FIG. 16, it is necessary to put the SE signal to the levelHI at the time T2″ before putting the RSTR signal to the level HI, forreflecting the data of the slave latch on the NOR output. Then, the SEsignal is desirably put to LO before the RSTR signal is put to the levelLO. FIG. 16 shows a control example where the SE signal is put to thelevel LO at time T6″ before the RSTR signal is put to level LO (timeT6). In this case, the data is reflected to the master-slave latch inthe next stage through a normal pass (data pass). In a case where thesetting of the data through a scan pass is more effective, control forputting the SE signal to LO may be conducted after the RSTR signal hasbeen put to the level LO.

Although not illustrated, the scan function can be applied also in acase of control by the complementary signal due to the RSTR signal andthe RSTRb signal, as in FIG. 13. In this case, the scanning circuit asdescribed above may be added to the part for the input D and the partfor the output Q.

While FIG. 10 to FIG. 16 show constitutional examples of themaster-slave latch, the invention is applicable also to latch circuitshaving other forms. FIG. 17 is an example of a pulsed-latch circuit. Thepulsed-latch circuit is a circuit in which a clock signal CLK and adelayed clock signal formed from passing the clock signal CLK through adelay circuit comprising three stages of inverters, are inputted to anNAND circuit, thereby generating a pulse upon rising of the clocksignal, opening the transmission gate TG3 by using the pulse CLKI andthe inverted pulse CLKIb inverted through the inverters and transmittingthe input D to the output Qb in the succeeding stage. Since thetransmission gate TG3 is closed upon completion of the pulse, thepulsed-latch circuit retains the data taken in the latch comprising thetwo stages of inverters disposed to the node ND3.

A constitutional example of applying the nonvolatile data retentionfunction to a pulsed-latch circuit is shown in FIG. 18A and FIG. 18B.FIG. 18A shows a first constitutional example. This is different fromthe constitution shown in FIG. 17 at first in that the data is retainedin the latch LT for data retention also during the power shutdown stateby supplying the power from the power line for data retention VSS_SIG,and further by the fact that the pulse generator is constituted as anillustrated AND-NOR type circuit for controlling the pulse generator bythe control signal RSTR, and by the fact that the power line for dataretention VSS_SIG is used at least for the low potential power on theside of NOR, and the power line for data retention VSS_SIG is used forthe low potential side power of the inverter that drives the pulse CLK1.In the example of FIG. 18A, the output Q is adapted as positive logic byproviding an inverter to the input D. While this causes a delay for onestage of the logic gate, the positive logic can be transmitted to thesucceeding stage and, further, more stable operation is possible for thefluctuation of the input data. For example, it provides high immunityfor input signal fluctuation, even when the input D is at a higherpotential than the high potential side power VDD due to noise. In thiscase, without this inverter, since the source-gate voltage difference ofthe transmission gate TG3, which should normally be in the OFF state,exceeds its threshold voltage, an invalid signal can be transferred tothe succeeding stage. A constitution in which the input D is outputtedafter inversion, as shown in FIG. 17, without provision of the inverteris also possible. By using the power line for data retention VSS_SIG forthe low potential side power of the driver NOR2 for driving thetransmission gate TG3 and INV4, since the power can be applied alsoduring power shut-down, it provides an effect capable of exact control.In this constitution, since the control signal can be constituted onlywith the RSTR signal, it provides an effect of facilitating the placingand routing by using CAD.

FIG. 19 is an operation waveform chart showing the operation and thecontrol method for the nonvolatile pulsed-latch circuit shown in FIG.18A. At time T1, since the control signal RSTR=LO, this shows a clockrising state in the normal operation. This is because the NOR gate NOR2shown in FIG. 18A outputs under inversion the pulse NDCK1 as it is in acase where the control signal RSTR=LO. Corresponding to the rising ofthe clock signal CLK, the pulse clocks CLKI and CLKIb generated by thepulse generator PG1 are put to the level HI and level LO, respectively.The pulse width is equal to a delay by the three stage inverter chain.When the pulse clock CLKI is put to LO and CLKIb is put to HI, thetransmission gate TG3 is turned ON and the input data D is outputted. Atthe same time, data is transmitted to the node NV in the nonvolatilecircuit NVC in the constitution shown in FIG. 18A.

Now, a description will be made of the operation of conducting powershut-down and retaining data in the nonvolatile circuit NVC. At time T2,the RSTR signal is at first put to the level HI. Then, NOR gate NOR2outputs the level LO irrespective of the level of the pulse NDCKI.

Subsequently, power shut-down control is conducted at time T3. Like theexample in FIG. 11, it is assumed herein that the potential of thevirtual power line VSSM rises to a higher potential due to a leakagecurrent in the internal circuit under the control of putting the PSWGATEsignal to LO. The interval between the times T3 and T2 is set as a timesufficient to retract whole data of the nonvolatile FF NVFF in the chip.The timing control can be conducted by the same method as the timingcontrol disclosed with reference to FIG. 11.

When power shutdown control is conducted, the potential of the virtualpower line VSSM increases and other retained data than in thenonvolatile circuit NVC is eliminated. On the other hand, since thepower for the nonvolatile circuit NVC is supplied from the power linefor data retention VSS_SIG, the node NV in the nonvolatile circuit NVCcan be retained continuously at a desired value.

Next, power-on sequence by turning on the power switch will bedescribed. In this case, the PSWGATE signal is driven to the level HI attime T4. Then, the level for the virtual power line VSSM is graduallydriven to 0 V and the data is transferred from the nonvolatile circuitNVC to the output Q. Since the power supply for the driving circuits ofthe clock signal CLK is also shut down, the level LO for the clocksignal CLK cannot be kept exactly at the ground level (0 V). However, itis desired to control the clock signal CLK so as to rapidly output thelevel LO after the power is supplied.

Subsequently, after confirming that the power switch has been turned ONcompletely and the level of the virtual power line VSSM has been put to0 V, the RSTR signal is put to LO at time T6. Thus, the NOR gate NOR2outputs under inversion the NDCK1 as it is. Since it is necessary for asufficient interval between times T5 and T6 to completely turn ON thepower switch, it can be controlled by using, for example, an acknowledgesignal from a power switch controller. Then, the normal operation of thepulsed-latch circuit of intaking data at the rising edge of the clock,as shown at time T7 and T8, can be attained.

This can provide a data retention mechanism upon power shut-down withoutsubstantial deterioration for the characteristics of the pulsed-latchcircuit, and this can provide the advantage of data retention upon powershut-down at a reduced cost by the application of the pulsed-latchcircuit to the system LSI.

FIG. 18B shows another example of the pulsed-latch circuit. This isdifferent from the constitution shown in FIG. 17 in that the latch LTfor data retention is connected with the power line for data retentionVSS_SIG to make the data nonvolatile and a transmission gate TG4 isdisposed to the connection route between the node ND3 and the node NVfor the nonvolatile circuit NVC. In this case, two signals RSTR andRSTRb are necessary for the nonvolatile control signal. In thisconstitution, since the number of circuits requiring the power line fordata retention VSS_SIG can be minimized, this can provide an effect ofenhancing the current supply performance to the pulse generator PG2requiring large current for the operation.

FIG. 20 shows an example of a circuit for providing a scan function tothe nonvolatile pulsed-latch circuit shown in FIGS. 18A and 18B. Thiscan be attained by replacing the nonvolatile circuit NVC incommunication with the node NV in FIGS. 18A and 18B with the nonvolatilecircuit NVC shown in FIG. 20. In normal operation, the function of thepulsed-latch circuit is attained by putting the clock signal forscanning CLKS to the level LO and the inverted clock signal for scanningCLKSb to the level HI. On the other hand, for sending the data by thescan function, the scan input signal SI is transferred to the node NVBby setting the scan clock CLKS to level HI and the inverted clock signalfor scanning CLKSb to the level LO, and then the data retained at thenode NVB is transferred to the scan output SO by setting the clocksignal for scanning CLKS at the level LO and the inverted clock signalfor scanning CLKSb at the level HI. In the case of using the scanfunction, it is necessary that the input D cannot be taken by puttingthe clock CLK in the pulsed-latch circuit of the system to LO foravoiding the effect of the input D of the pulsed-latch circuit.

Although not illustrated, the scan function may be attained also byreplacing the selector circuit capable of selecting the scan input SIand the usual data input D by the SE signal, as shown in FIG. 15, withthe input part shown in FIG. 18A or FIG. 18B, and, further, by applyingan additional circuit outputting the output Q and the scan output SO, asshown in FIG. 15, in the output part in FIG. 18A or FIG. 18B.

FIG. 21 shows an example of a sense-amplifier based flip-flop circuit.The low potential side power for the nonvolatile circuit NVC is a powerline for data retention VSS_SIG and the low potential side power forother circuits is a virtual power line VSSM.

FIG. 22 is an operational waveform chart showing the operation and thecontrol method of the nonvolatile sense-amplifier based flip-flopcircuit shown in FIG. 21. At time T1, since the control signal RSTR=LO,the control signal RSTRb=HI, the control signal CLKB=LO, and the controlsignal CLKA=LO, the state of clock rising state during the normaloperation is shown. The input D is taken in accordance with the risingof the clock signal CLKC and the output Q is outputted corresponding tothe value.

Now, description will be made of a case in which power shutdown isconducted. At first, the clock signal CLKC is put to the level LO suchthat the data of the input D of the sense-amplifier based flip-flopcircuit is not captured. The control signal CLKB is put to the level HIat time T11 to intake the level data at the node Qb to the nonvolatilecircuit NVC and then the control signal CLKB is put to the level LO.This electrically disconnects the nonvolatile circuit NVC from theflip-flop main body. Also, in this case, the control signal CLKA iscontrolled to the level LO. Then, the control signal RSTR is put to thelevel HI and the control signal RSTRb is put to the level LO forproviding a feedback route from the nonvolatile circuit NVC at time T2.This state means that the electrical route of the node Q and the node Qbto the ground is controlled by the feedback route from the nonvolatilecircuit NVC. While FIG. 22 shows an example of controlling the controlsignal RSTR and the control signal RSTRb substantially simultaneously,the control order of asserting these control signals has no particularrestriction. This is because the data necessary for the nonvolatilecircuit NVC has already been retained. Further, as shown in FIG. 11 andFIG. 13, it is possible to be controlled by two signal lines from theoutside, or the RSTRb signal may be generated in the flip-flop by usingan inverter circuit.

Subsequently, power shutdown control is conducted at time T3. Like theexample in FIG. 11, it is assumed that the potential of the virtualpower line VSSM rises toward the high potential side due to the leakagecurrent in the internal circuit by the control of putting the PSWGATEsignal to LO. A sufficient period is set for the internal operationbetween times T3 and T2 sufficient to retract the data of thenonvolatile FF in the chip. The timing control can be conducted by thesame method as the control used for FIG. 11.

When the power shutdown control is conducted, the potential for thevirtual power line VSSM rises and other retention data than in thenonvolatile circuit NVC are eliminated. In this case, since the powerfor the nonvolatile circuit NVC and the control signal CLKB is suppliedfrom data retention circuit VSS_SIG, the internal nodes SO and SOb inthe nonvolatile circuit NVC can be retained continuously at a desiredvalue.

On the other hand, in the power on state, the PSWGATE signal is drivento the level HI at time T4 firstly. As a result, the potential of thevirtual power line VSSM is gradually driven to 0 V and the data istransferred from the nonvolatile circuit NVC to the output Q. Further,since the power is shut down also for the driving circuit of the clocksignal, the LO level for the clock signal CLKC cannot be kept exactly atthe ground level (0 V). However, it is desired to control the clock CLKCsuch that the level LO is outputted rapidly after the re-supplying ofthe power.

Then, after confirming that the power switch has been turned ONcompletely and, therefore, that the potential of the virtual power lineVSSM has been driven to 0 V, the control signal CLKA is put to the levelHI at time T12. Since the data in the nonvolatile circuit NVC is writtenback to the nodes Q and Qb, the output is determined. After putting thecontrol signal CLKA to the level LO, the RSTR signal is put to the levelLO and the RSTRb signal is put to the level HI at time T6. The statewhere the RSTR signal is at LO and the RSTRb signal is at HI indicatesthat scan inputs I and Ib are selected upon writing to the nodes Q andQb. Therefore, it is possible that these signals are controlled asfollows: the RSTR signal is put to LO and the RSTRb signal is put to HIfor the case of scanning, and the RSTR signal is put to HI and the RSTRbsignal is put to LO in other cases. A sufficient period is necessary forthe interval between times T5 and T6 sufficient to turn ON the powerswitch completely. For this purpose, control may be conducted by using,for example, an acknowledge signal from the power switching controller.

Subsequently, the normal operation of the conventional sense-amplifierbased flip-flop, which captures the data at the rising edge of theclock, as shown in time T7, T8 is attained.

This constitution provides a data retention mechanism during powershut-down without substantial deterioration of the characteristics ofthe sense-amplifier based flip-flop and provides the advantage ofattaining data retention during power shut-down at a reduced cost byapplying the sense-amplifier based flip-flop to a system LSI.

FIG. 23A and FIG. 23B show modified examples of the connection of apower line for data retention VSS_SIG to a storage element for dataretention SEC. The storage element for data retention SEC is acollective name for circuit elements to be supplied with power by thepower line for data retention VSS_SIG in each of FIGS. 13, 15, 18, 20and 21, which includes, for example, a nonvolatile circuit NVC and aclocked inverter CINV1 (FIG. 11). FIG. 23A shows an example of switchingthe power supply to the storage element for data retention SEC by theRSTR signal and the RSTRb signal between the virtual power line VSSM andthe power line for data retention VSS_SIG. This provides an effectcapable of obtaining a desired large current in a case where it isintended to supply a large current to the storage element for dataretention SEC by enabling the power supply from the virtual power lineVSSM. For example, in the case of the pulsed-latch circuit shown in FIG.18A, the pulse generator PG1 requires a great amount of current, and useof the constitution described above provides an effect capable ofsupplying necessary and sufficient operation current during operation ofthe pulse generator PG1 and not causing deterioration in the speed.Since the data can be retained only by a minute current (standby mode),connection is made with the power line for data retention VSS_SIG toattain reduced current consumption.

FIG. 23B shows a modified example of conducting ON-OFF control for theconnection of the virtual power line VSSM and the power line for dataretention VSS_SIG by the RSTRb signal. In a case where a large currentis necessary, it is connected with the virtual power line VSSM to obtaina desired large current. On the other hand, a minute current is suppliedfrom the power line for data retention VSS_SIG during the standby mode,thereby attaining reduced power consumption.

While the two modified examples show the case of control by the RSTRsignal and the RSTRb signal, control may be conducted by an independentsignal line separately from the signals. In this case, an independentsignal line is added by the number of one in a cell image shown in FIG.9. In a case of control by the independent control line, although thenumber of pins is increased, since the current can be controlledindependently of the RSTR signal, the power can be shut down on the sideof the power line for data retention VSS_SIG and can be kept at asubstantially high impedance state during operation. This provides aneffect capable of attaining further reduced power consumption.

FIG. 24 shows an example of controlling by means of one control signalNVCTL using a pulsed-latch circuit in practicing the control of thepower line for data retention VSS_SIG shown in FIG. 23. This is amodified example of the pulse generator PG1 shown in FIG. 18A. Thisexample is based on the premise that nonvolatilizing control is attainedat the control signal RSTRb=LO by using the RSTRb signal. In a case ofusing the circuit shown in FIG. 23B, the number of the control signalline may be reduced to one with such a constitution. The operation inthis case corresponds to that in FIG. 19 in which the RSTR signaltherein is changed with the RSTRb signal as an inverted signal thereof.Also, in this case, operation of other signals and a mutual relation maybe controlled in the same manner. It will be apparent that a desirednonvolatile control can be attained in FIG. 23A also by reversingconnections between the RSTRb signal and the RSTR signal.

FIGS. 25A to 25C show examples of forming the power line for dataretention VSS_SIG. In these examples, for further reducing the powerconsumption during the standby mode, the value for the power line fordata retention VSS_SIG can be controlled dynamically. FIG. 25A has aconstitution capable of selecting the route to the power line for dataretention VSS_SIG between the route connected with the ground GND by wayof an N-type MISFET MNTC1 and a voltage source, and a route connectedwith the ground GND only by way of an N-type MISFET MNTC2 by using GATA1signal and GATA2 signal, respectively. As shown in the drawing, forcontrolling the transistor, it is desirable to use a MISFET in an I/Ohaving a large gate dielectric film thickness. Further, FIG. 25B showsan example of obtaining the voltage source in FIG. 25A by a diodeconnection, while FIG. 25C shows an example of a circuit for supplying aconstant voltage from a constant voltage generator using a referencevoltage generator VREF.

FIG. 26 is a graph showing an operation waveform in a case of applyingthe VSS_SIG generation method shown in FIGS. 25A to 25C to themaster-slave latch shown in FIG. 11. The method has a feature in thatthe value of the power line for data retention VSS_SIG is controlled toan intermediate level from time T9 to time T10. It is desired thatcontrol is conducted at time T9 after complete power shut-down and thelevel is returned to 0 V at time T10 before entering the power applyingoperation. This is conducted for preventing destruction of retained datain the nonvolatile circuit NVC by the effect of the noise caused by theoperation of the internal circuit upon shut-down and power-on sequence,which enters the power line for data retention VSS_SIG. Time T9 may becontrolled after shut-down of power at time T3 based on a signalindicating the complete shut-down of the power (for example, acknowledgesignal) generated from a power switching controller. For determining thetime T10, it is possible to adopt a method of decreasing the drivingpower of a driver MNTC2 in FIG. 25A to FIG. 25C, measuring a time untilthe potential at the basis of the power line for data retention VSS_SIGreaches a predetermined threshold value or lower and turning the powerswitch to ON after a period several times as long as the measured time.

Further, in accordance with the invention, an increase in the speed anda reduction in the power consumption can be attained further by usingtwo kinds or more of transistors. FIG. 27 shows a modified example of amaster-slave latch as shown in FIG. 11. The constitutional example has afeature in using a MISFET having a low threshold voltage for amaster-slave latch that operates during normal operation and a logicgate LVTINV and a transmission gate LVTTMG using the same low thresholdvoltage MISFETs. This can increase the speed of the normal operation. Onthe other hand, for the circuits necessary during the standby mode, theleakage current can be suppressed by using a MISFET having a highthreshold voltage and a logic gate HVTINV and a transmission gateHVTTMG, which consist of high threshold voltage MISFETs. Further, in acase where the gate dielectric film thickness of a MISFET constituting acircuit necessary in the standby mode (INV1, CINV1, NVC) is madethicker, it also provides an effect capable of saving the gate leakagecurrent.

In this case, it is desired that the selection of the gate dielectricfilm thickness is based on that of a SRAM. It is expected that gateleakage currents for the memory cell in a SRAM will result in problemsin the future. For example, in a case where the EOT (equivalentgate-dielectric thickness) for the MISFET used in the core is about 1.5nm, the gate leakage current flowing through the SRAM can be decreaseddrastically by increasing the thickness of the dielectric film of theSRAM gate to about 2.0 nm to 2.2 nm by EOT. This is because the gateleakage current decreases by one digit on every increase in thethickness of 0.2 nm for EOT. In view of the above, in a system LSIfabricated by a multi-gate insulative film process (multi TOX process)which realizes such a SRAM, when the data retention part (INV1, CINV1,NVC) of a nonvolatile FF is constituted by using a MISFET having largethickness such as used for a SRAM memory cell, the nonvolatile FF withless leakage can be attained advantageously without additional processsteps.

Such a modification is applicable also to a pulsed-latch circuit asshown in FIG. 18 or the sense-amplifier based flip-flop circuit as shownin FIG. 21. Also, in this case, a MISFET of low threshold voltage may beused in circuits other than a storage element for data retention SEC, orthe gate-dielectric thickness of the transistor of the storage elementfor data retention SEC may be made identical with that of a SRAM.

FIGS. 28A to 28D show examples of adding a capacitance element to thenonvolatile circuit NVC. This is for improving various kinds of noisemargins such as noise immunity against α-particles, neutron, cosmicrays, etc. in a nonvolatile circuit NVC. Particularly, the noise errorbecomes remarkable when the applied voltage for the storage elementcircuit SEC is reduced in order to reduce the leakage current bycontrolling the power source line for data retention VSS_SIG, as shownin FIG. 26, during the standby mode. This capacitance element isconnected between the nodes NV and NVb of the nonvolatile circuit NVC inFIG. 11, FIG. 13, FIG. 15, FIG. 18, FIG. 20, and FIG. 21. In this figurethe latches including two inverters are shown, but it is applicable inthe same manner in a case where the latches are constituted with clockedinverters, as shown in FIG. 11, or a switching MISFET is provided. FIG.28A shows an example of providing a capacitance element between the nodeNV and the node VCb and FIG. 28B is an actual example thereof. As shownin FIG. 28B, by bidirectionally connecting a MISFET as capacitanceelements, since one of the MISFETs always functions as the capacitanceelement in accordance with the value for NV and NVb, a stable operationis possible.

FIG. 28C shows an example of a capacitive coupling between storage nodesNV, NVb and the power line for data retention VSS_SIG. The virtual powerline VSSM is not suitable to be coupled, because it results in manynoises upon power-on and shut-down of power and noises during operation.Therefore, capacitive coupling to the power line for data retentionVSS_SIG is desirable. Such a capacitance element can be obtained byusing an N-type MISFET, connecting the gate of the N-type MISFET to thenode NV and the node NVb, and connecting the source and the drain to thepower line for data retention VSS_SIG. In a case of using a P-typeMISFET, connection between the gate and the drain and the source areinverted or reversed. Further, FIG. 28D shows coupling to the highpotential power source VDD. This can also be attained by using an N-typeMISFET, connecting the gate N-type MISFET to the high potential sidepower source VDD and connecting the source and the drain to the side ofthe node NV and the node NVb. In a case of using a p-type MISFET, theconnection between the gate and the drain and the source may bereversed. Application of them provides an effect of improving the noiseimmunity.

In a case of shut-down of the power line for data retention VSS_SIG, thecapacitance element may be disposed so as to avoid coupling to thevirtual power line VDDM wired in the cell.

FIG. 29 shows an example of the layout for standard cells for attainingthe present invention. This shows a so-called standard cell with 9-gridheight which can be laid out with nine minimum-width metals. This showsan example having VSSM wiring riding over the No. 0 track and the No. 1track, and VDD wiring riding over the No. 8 track and the No. 9 track.In a case of using metal of such a large width for the power line, it isnecessary to also enlarge the space in view of the condition in theresolution upon exposure, and the wiring is inhibited for the No. 2track and No. 7 track in many cases. Accordingly, No. 3 track, No. 4track, and No. 5 track are allocated to the wirings in the cell, and theNo. 6 track is allocated as the inter cell wiring channel.

For explaining the wiring structure of the transistors in the cell, twoinverters are shown in the drawing. One of them is a normal inverterwhich is supplied with power from the virtual power line VSSM. Thisinverter has an input terminal i1 and an output terminal o1. The otherof them is a nonvolatile inverter which is supplied with power by usinga power line for data retention VSS_SIG. This inverter has an inputterminal i2 and an output terminal o2. The normal inverter is connectedfrom the power supply metal (M1) in which two power sources (VDD andVSSM) are wired in the cell by way of an M0 wiring layer to a diffusionlayer (L). This corresponds to the view seen along line A-A′ in thefigure and a cross sectional view thereof is shown in FIG. 30A. As isapparent from the figure, the two power sources are connected with powerwiring. The drawing shows an example of leading from the second metal(M2) and the substrate power supply is used in common with the normalinverter and the nonvolatile inverter. While the substrate power sourcescan be constituted separately for the normal inverter and thenonvolatile inverter, this needs well isolation for the isolation of thesubstrate power sources to lower the area efficiency.

The cross sectional structure will be described simply. This exampleconsists of a triple well structure in which an N-type well DNW isprepared to a deep depth on a P-type substrate PSUB, on which a P-typewell PW for forming an N-type MISFET and an N-type well NW for forming aP-type MISFET are formed. In a case of adopting such a substratestructure, it is possible for a substrate bias control to control thesubstrate potential thereby decreasing the leakage current. When thesubstrate bias control is used, the absolute value of the thresholdvoltage is effectively increased. Therefore, the leakage current can bedecreased by controlling the substrate voltage lower than the sourcevoltage of the N-type MISFET in a case of the N-type MISFET and bycontrolling the substrate voltage higher than the power source voltageof the P-type MISFET in a case of the P-type MISFET. Also, in accordancewith the invention, the power consumption can be further reduced byconducting such substrate bias control during the standby mode. Althoughnot illustrated, it is also applicable to a so-called double wellstructure not provided with the N-well DNW.

The output O1 is connected to metal wirings M1 and M2 by way of viaholes after connecting the diffusion layers of the P-type MISFET and theN-type MISFET together. This corresponds to the view seen along lineB-B′ in FIG. 29 and the cross section is shown in FIG. 30B.

On the other hand, the nonvolatile inverter has a feature in that thepower source on the side of VDD is connected from the VDD power wiringby way of metal layer M0 and the ground side is wired from the pin ofVSS_SIG, which situated about at the center of the cell height. Thisconnection corresponds to the view seen along line C-C′ in the FIG. 29and the cross section is shown in FIG. 31A. As apparent from thedrawing, the source of the N-type MISFET is not connected with thevirtual power line VSSM. The output O2 is connected by way of the viahole VIA to the metal wirings M1 and M2 after connecting both of thediffusion layers of the P-type MISFET and N-type MISFET together. Thiscorresponds to the view seen along line D-D′ in FIG. 29 and the crosssectional view is shown in FIG. 31B.

FIG. 32 is a layout view of a first area AE1. A circumferential mainpower line (power ring region) is laid out so as to surround the firstregion AE1. Power lines VDD, power lines VSS, visual power lines VSSMand various kinds of control signals are wired. When a control circuitfor the standby mode STBYC and such are arranged below the power ringregion PR1 to PR8 in FIG. 38, the area can be utilized effectively.Since the main power line of the first metal layer and regions PR4 andPR8 are situated on both ends of the cell row, it is advantageous toprovide a MISFET for power shut-down. Since a MISFET for power shut-downrequires large a current supply performance, it is preferably laid outas plural MISFETs. Further, it is preferred that the power switchingcontroller, VSS_SIG generator and NVCTL control circuit for generatingthe control signal group of the nonvolatile circuit NVC shown in FIG.25A to FIG. 25C are laid out below regions PR1, PR3, PR5, and PR7 atfour corners of the power ring region.

Further, FIG. 32 shows an example in which power line MW1 to power lineMW9 at the second metal layer for power reinforcing are laid out in thelongitudinal direction. In the drawing, there are three power lines(power line VDD and VSS and virtual power line VSSM) as a group of powermain lines extending in the direction Y of the drawing (referred to as“group of longitudinal main line”), but they are not restricted tothree. Further, in an actual layout, various power supply lines can belaid out using multiple layers, or such power supply lines can be laidout only with one wiring layer (for example, M2 layer).

In placing and routing by using a CAD, layout is facilitated by theconstitution of arranging by using cells CELL in which only thelongitudinal main lines are laid out each at an equal interval.Generally, MISFETs are not prepared, but only the power wirings are laidout in the cells CEL1.

In a case where the control signal NVCTL of a number of nonvolatile FFare driven only by a single driver of the control circuit in the standbymode CTBYC, the driving force cannot sometimes be obtained sufficiently.In this case, a repeater cell is advantageously disposed in the cellCEL1. Since the power line VSS which is always supplied with power canbe wired in the cell CEL1, it is possible to dispose a driver capable ofoperating also in the standby mode. For the layout of the driver, wiringmay be conducted as the wiring of the nonvolatile inverter on the sourceof NMOS in the layout of FIG. 29.

FIG. 33 shows a constitutional example of an LSI chip to which theinvention is applied. The LSI chip is shown as a block diagram in a caseof application to an information processing device, particularly, amicro processor. The LSI chip (system LSI) is preferably formedmonolithically on one single semiconductor substrate.

The system LSI has a first region AE1, a second region AE2 and a thirdregion AE3 as regions capable of controlling the power supplyindependently. The first region AE1 comprises a processor CPU, embeddedcircuit modules IP1 and IP2, a system bus SYSBUS, and a clock generatorCPG. The power supply of this region is controlled by a power switchSW1. It is preferable that all flip-flops or latches in the first regionAE1 are constituted with a nonvolatile FF. But, it is also possible toconstitute only a minimal number of the flip-flops or latches necessaryfor retaining the status with the nonvolatile FF. The second region AE2contains a built-in user memory URAM. The power supply of this region iscontrolled by a power switch SW2. Finally, the third region AE3 containsa control circuit for standby mode STBYC. This region is always suppliedwith power so long as power is supplied to the system LSI. In this case,the power switches SW1 and SW2 are supposed to be put between the groundpotential VSS and the virtual ground potential VSSM for each of theregions. But of course they may be put between the power supply VDD andvirtual power supply VDDM for each of the regions. Particularly, in acase of providing a voltage regulator, the voltage regulator can also beused in place of the power switch. Further, it may be disposed bothbetween the ground potential VSS and the virtual ground potential foreach of the regions and between the power supply VDD and the virtualpower supply VDDM for each of the regions.

The CPU controls the entire system LSI. The embedded circuit module IP1is not necessary when the CPU fetches the instruction, for example, anaccelerator for MPEG. The embedded circuit module IP2 is necessary whenthe CPU fetches the instruction, for example, a bus state controller.The system bus SYSBUS is connected with each of the circuit modulesincluding the CPU and it includes a not illustrated data bus and addressbus. The clock generator CPG receives the clock signal RCLK andgenerates an internal clock signal ICLK. The internal clock signal ICLKis supplied to each of the circuit modules and the system LSI operatesin accordance with the internal clock signal ICLK. The built-in usermemory URAM has a large capacity and retains necessary data such as dataunder processing. In the constitutional example of FIG. 33, each of thecircuit modules contained in the first region AE1 is collectivelyarranged and each of the circuit modules contained in the second regionAE2 is collectively arranged. With such an arrangement, since the powerswitches SW1 and SW2 can be provided in common with plural circuitmodules, the area can be decreased. Further, in FIG. 33, the embeddedcircuit modules disposed in the first region AE1 can also be arranged indifferent regions independently for enabling power shutdown relative toeach other. In this case, since the power shut-down control can beconducted on every module if they are not in use, power shut-down forthe embedded circuit modules not in operation can be conducted evenduring operation of the CPU to provide an effect capable of saving theleakage current during operation.

In the standby mode utilizing the nonvolatile FF of the invention(referred to as “first standby mode STBY1”), the power switch SW1 is putto the off state and the power switch SW2 is kept in the ON state. Sincethis shuts down the power supply to the processor CPU, the embeddedmodules IP1 and IP2 and the clock pulse generator CPG, the currentconsumption can be decreased. Also in this case, since the power can besupplied to all of the nonvolatile FF in the first region AE1, the datacan be retained continuously.

The transition operation will be described. The internal data in thefirst region AE1 is retained by the nonvolatile FF. Further, cash data,etc. are retracted to the built-in user memory URAM as required. Thenonvolatile FF is supplied with power and the control signal by thecontrol circuit in the standby mode STBYC in the third region AE3. Then,the power switch control signal SW1-C puts the power switch SW1 to theOFF state to stop the supply of current to each of the circuit modulescontained in the first region AE1. Since the main power switch SW2 iskept ON, current is supplied to the circuit modules to the nonvolatileFF in the first region AE1 and the circuit modules in the second regionAE2, and the internal data of the system LSI is retained. Thus, theinterruption upon returning from the first standby mode can be conductedby returning the data of the nonvolatile FF or the data retained in theinternal built-in user memory URAM to a predetermined circuit in thefirst region AE1 by the interruption request from the outside. In a casewhere the interrupt request is given, the control circuit in the standbymode STBYC turns the power switch SW1 to ON as explained, for example,with reference to FIG. 11 and FIG. 12. After the power is supplied tothe first region AE1, the data retained in the nonvolatile circuit NVCof the nonvolatile FF is reflected to the output of the nonvolatile FF.Therefore all states of the random logic of the first region AE1 arerecovered to the state before power shutdown. In a case where the dataretracted to the built-in user memory URAM is present, the retractedinternal data of the system LSI is returned to the first region AE1.

Since the operation is conducted in a shorter time compared with theresetting sequence which requires booting of software, such as an OS, itcan be returned at a higher speed compared with U standby losinginternal data where the internal data is eliminated. While a descriptionhas been made with respect to an example in which the internal data isretracted to the build-in user memory URAM, it can also be retracted toan external memory.

Further, in the system LSI, another standby mode, for example, anexistent software standby (refer to as “second standby mode STBY2”) or Ustandby (refer to as “third standby mode STBY3”) mode can be usedtogether. This can set a low current mode flexibly depending on thestate of the system LSI being used. FIG. 34 shows a table for each ofthe modes.

The first standby mode STBY1 is a state where the power for the firstregion AE1 is shut down, and power is supplied but the clock is stoppedin the second region AE2. Since the internal data in the first regionAE1 can be retained by the nonvolatile FF, the internal data is retainedand can be returned by an external interrupt. Accordingly, for thereturning time, only the time up to the restarting of the clock, whichis done in parallel with the operation time of the power switch, may betaken into consideration, and it can be returned in about severalhundred μseconds. Transition to the first standby mode can be attainedby setting a mode setting register STBCR of the control circuit in thestandby mode STBYC. In the first standby mode, since the power for mostof the circuits in the first region AE1 is shut down by the powerswitch, the current consumption is suppressed to about 100 μA.

In the second standby mode STBY2, while the power is supplied to all ofthe first region AE1, the second region AE2 and the third region AE3,distribution of the clock signal to the first region AE1 and the secondregion AE2 is stopped. Accordingly, since the circuit modules in thefirst region AE1 and the second region AE2 are not operated, the systemcan stand by with a consumption power of about the transistor leakagecurrent. Also in this case, since the internal data can be retainedcontinuously, the internal data is nonvolatile. Further, for thereturning time, since returning can be conducted by the interruptionprocessing described above, it may be only about the time for restartingthe clock and it can be returned in about several hundred μseconds. Thetransition to this mode can also be attained by setting the mode settingregister STBCR of the control circuit in the standby mode STBYC.

The third standby mode STBY3 is a mode for shutting down the power forall regions other than the third region AE3; and, while the consumptioncurrent is about 10 μA, since the internal data is evaporated, it can bereturned only by resetting and it needs about several hundredmilliseconds for returning. The transition to this mode can also beattained by setting the mode setting register STBCR of the controlcircuit in the standby mode STBYC.

As can be seen from the table in FIG. 34, since the first standby modeSTBY1 and the second standby mode STBY2 are different only with respectto the current consumption, the first standby mode and the secondstandby mode can be collected into one low current mode. Further, powerand clock signals are supplied to all of the first region AE1, thesecond region AE2 and the third region AE3 during normal operation, andsupply of the power is shut down to all of the circuits upon turning OFFof the power.

Various combinations of mode shown are possible herein for the standbymode. In this case, the constitution of the system LSI is also modifiedto such an extent as necessary for the combination. For example, in asystem LSI not having a third standby mode, the second region AE2 inFIG. 33 is eliminated and the circuit module in the second region AE2 isdisposed in the third region AE3. Further, instead of the power switchin the system LSI, the power may also be shut down by a power controlcircuit external to the system LSI. Further, instead of controlling allnonvolatile FF in the first region AE1 with one control circuit in thestandby mode STBYC, a standby control circuit may also be provided onevery module.

FIG. 35 is a view showing the transition between each of the modes. Thepower off mode transits to the normal operation mode by turning ON thepower. Conversely, the normal operation mode transits to the power offmode by turning off the power.

The normal operation mode transits to the third standby mode STBY3 bysetting the register STGCR. Conversely, the third standby mode STBY3returns to the normal operation mode by resetting. The third standbymode STBY3 transits to the power off mode by turning OFF the power.

The normal operation mode transits to the first standby mode STBY1 bysetting the register STBCR. Conversely, the first standby mode STBY1transits to the normal operation mode by external interruption orresetting. The first standby mode STBY1 transits to the power OFF modeby turning OFF the power.

The normal operation mode transits to the second standby mode STBY2 bysetting the register STBCR. Conversely, the second standby mode STBY2transits to the normal operation mode by external interruption orresetting. The second standby mode STBY2 transits to the power OFF modeby turning OFF the power.

FIG. 36 shows the constitution of the control circuit in the standbymode STBYC for controlling the transition and returning to and fromvarious types of standby modes. Description is to be made at first to acase of applying the nonvolatile FF of the invention to flip-flops andregisters by the required minimum number. The control circuit in thestandby mode STBYC is connected with a system bus SYSBUS for reading andwriting to and from the internal register and inputted with an interruptrequest signal IRQ, a reset signal RSK and a clock signal RCLK. Theoutput from the control circuit for the standby mode STBYC includes anonvolatile control signal NVCTL, a power line for data retentionVSS_SIG, an interrupt signal INTR notifying interruption to the CPUafter returning from the second standby mode, a CPU execution startaddress RST-VEC (the first address for beginning the process when theCPU resumes), a reset signal RST1 for the first region AE1 and a controlsignal WS1-C for the power switch SW1, a reset signal RST2 for thesecond region AE2 and a control signal SW2-C for the power switch SW2.While the interrupt signal INTR is directly connected with the CPU inFIG. 33, it may be connected, for example, by way of an interruptcontroller to the CPU.

The control circuit in the standby mode STBYC has a standby mode controlregister STBCR and a boot address register BAR as registers capable ofreading and writing from and to the system bus SYSBUS. Reading andwriting from the system bus SYSBUS are controlled by a decoder. Thestandby mode control register STBCR retains a value corresponding to thecurrent standby mode. Further, writing from the system bus STSBUS to thestandby mode control register STBCR forms a transition request to eachof the corresponding low current modes. In this example, the controlcircuit in the standby mode STBYC is constituted so as to controltransition to the first standby mode, the second standby mode and thethird standby mode, or for returning from each of the modes. Further,transition to or returning from the first standby mode can be conductedalso by directly sending a clock stop command from the CPU to the clockpulse generator CPG.

Upon returning from the second standby mode and releasing a reset state,the boot address register BAR retains the address of the instructionthat the CPU should execute first. In this example, the transitionrequest to the second standby mode is given by writing to the standbymode control register STBCR, but the transition can be requested also byusing a special command such as sleep or standby, or a combination ofthe standby mode control register STBCR and the special instruction. Inthis case, the CPU can instruct by sending the transition request by wayof an acknowledge signal for a sleep request, which is not illustratedhere, to the control circuit in the standby mode STBYC.

A synchronizer SYNC included in the control circuit for the standby modeSTBYC synchronizes the interrupt request IRQ from the outside of thechip with the external clock signal RCLK. A current mode controlsequence circuit STBYC-FSM judges the necessity for the transition andreturn of the standby mode and outputs the sequence for transition andreturn as required. The input is a value of the standby mode registerSBCR, the interrupt request IRQ, the status register STATE indicative ofthe step under execution in the sequence during transition and return,and the output is an output of the control circuit in the standby modeSTBYC and a second standby mode signal STBY2-MODE that indicates whetherthe current state is the second standby mode or not.

Upon returning from the second standby mode when receiving the interruptrequest signal IRQ from the outside, it is necessary to conduct aninterruption corresponding to the interrupt request signal IRQ afterreturning the data retracted to the built-in user memory URAM or theexternal memory to each of the circuit modules in the first region AE1.The interruption is conducted by executing a predetermined instruction.Accordingly, upon returning from the second standby mode, it isnecessary to retain the address of the memory which stores aninstruction to be conducted at first after returning. Thus, the bootaddress register BAR is disposed for retaining the address of the memorystoring an instruction to be executed at first upon returning from thesecond standby mode, and an execution starting address is set to theboot address register BAR upon transition to the second standby mode. Itis also possible to set the execution starting address upon returningfrom the second standby mode so that it is always identical. In thiscase, it is possible to constitute with a hard wired structure whilesaving setting of the execution address upon transition to the secondstandby mode. According to the constitution shown in FIG. 36, a softwaredesigner can freely set the execution start address after a return bythe provision of the boot address BAR and can locate the programnecessary for the return of the second standby mode at an optionalposition in a memory space.

On the contrary, since the return from the third standby mode alwaysinvolves a resetting, the boot address INIT-VEC is executed at first. Inthe constitution of FIG. 36, a selector SELL is provided, a secondstandby mode signal STBY2-MODE is outputted from the current modecontrol sequence circuit STBYC-FSM to select either the address storedin the boot address register BAR or the boot address INIT-VEC uponnormal resetting for the first address for beginning the process whenthe CPU resumes. This can attain the function of outputting the bootaddress INIT-VEC upon resetting for returning from the third standbymode and executing the instruction from the address retained in the bootaddress register BAR only upon returning from the second standby mode.In the return from the first standby mode, after starting the supply ofthe internal block signal, an instruction is read out from the addresscorresponding to the kind of interrupt request IRQ in the same manner asin the interruption processing which occurs during normal operationmode.

In the constitution of FIG. 36, the execution start address upon returnfrom the second standby mode or the third standby mode is decided by thecontrol circuit in the standby mode STBYC, and it is inputted to theCPU. On the other hand, it is also possible to provide a register forretaining the execution start address after returning to the CPU andconduct retraction and a return for the register by the hardware usingthe nonvolatile FF.

While the description has been directed to a control circuit in thestandby mode STBYC in a case of adopting a nonvolatile FF partially, allFF and registers included in the first region AE1 may be replaced with anonvolatile FF. In the system described above, since data in the CPU(circuit modules) are entirely retained upon return by interruption, itis no longer necessary to write the value by the CPU execution startaddress RST-VEC. Accordingly, such a system can be constituted whilesaving the boot address register BAR and the selector SELL.

The sequence of transition to the second standby mode STBY2 and thereturn to the normal operation mode will be described with reference toFIG. 37 and FIG. 38. At first, FIG. 37 shows a sequence transiting fromthe normal operation mode to the second standby mode STBY2. In cycleC1-1, a value STY2 meaning the second standby mode is written from thesystem bus STYBUS to the standby mode control register STBCR. In thecycle C1-2, the control circuit in the standby mode STBYC reads thevalue and puts the module stop signal MSTP “1” through the system SYSBUSto stop the supply of clocks to the first region AE1 in the cycle C1-3.Then, in the cycle C1-4, it puts the second standby mode signalSTBY2-MODE and the nonvolatile FF control signal NVCTL to “1” andretracts the data of the flip-flop in the modules in the first regionAE1 to the data retention part of the nonvolatile FF. Subsequently, itinforms the current mode control sequence circuit STBYC-FSM (a finitestate machine for selecting standby current consumption mode) that thecontrol signal NVCTL of the nonvolatile FF has completed control to allthe nonvolatile FF by putting the acknowledge signal NVACK to “1”. Inthe cycle C1-5, it detects that the acknowledge signal NVACK is at “1”and in the cycle C1-6, the current mode control sequence circuitSTBYC-FSM conducts control by putting the control signal SW1-C of thepower switch SW1 to “0”. As a result, the power for the first region AE1is shut down and the ground level VSSM1 of the first region AE1increases gradually. Complete shutdown of the power switch SW-1 isdetected by the fact that the control signal SW-C is completely “0” andthis is indicated by the ACK1 signal to the current mode controlsequence circuit STBYC-FSM. In the cycle C1-7, the current mode controlsequence circuit STBYC-FSM detects that the ACK1 signal has turned to“0” and, subsequently, the current mode control sequence circuitSTBYC-FSM conducts voltage control for decreasing leakage in thenonvolatile circuit for the power line for the data retention VSS_SIG ofthe nonvolatile FF. In this case, due to transmission of the voltagecontrolled state for the current mode control sequence circuit VSS_SIGto the current mode sequence control circuit STBYC-FSM by the ACK_VSIGsignal, the current mode control sequence circuit STBYC-FSM canrecognize the state of the nonvolatile FF. Thus, transition from thepower on state for power shutdown has been completed while retaining thedata in the nonvolatile FF.

FIG. 38 shows a sequence of returning from the second standby mode byinterruption. In the cycle C2-1, interruption occurs and then theinterrupt request signal IRQ is set to “1”. In the cycle C2-2, thecontrol circuit for the standby mode STBYC receives this and thenasserts the interrupt request after the return to the second standbymode INTR. At the same time, this control circuit conducts the operationof returning the voltage level of the power line for data retentionVSS_SIG to the ground. In the cycle C2-3, the current mode controlfinite state machine STBYC-FSM detects that the ACK_VSIG signal is at“0” and receives information that the power line for data retentionVSS_SIG is put to 0 V. Corresponding to the control of the ACK_VSIGsignal to “0”, the current mode control finite state machine STBYC-FSMturns the signal SW1-C for the power SW1 to “1” and turns ON the powerfor the first region AE1. Thus, the ground level VSSM1 of the firstregion AE1 is driven to 0 V. Then, when it is detected that the powerswitch has been turned to ON completely and the ACK1 signal turns to“1”, the current mode control finite state machine STBYC-FSM receivesinformation that the ACK1 signal turns to “1” in the cycle C2-5. Theoperation of restoring the data retracted to the nonvolatile circuit ofa nonvolatile FF to the original latch is conducted by turning the NVCTLto “0”, and this is started in the cycle C2-6. Completion of the datareturning in all nonvolatile FF is recognized from the fact that thenonvolatile FF control signal NVCKL has turned completely to “0”, whichis transmitted to the current mode control finite state machineSTBYC-FSM by turning the acknowledge signal NVACK to “0”. In the cycleC2-7, the current mode control finite state machine STBYC-FSM detectsthat the acknowledge signal NVACK has turned to “0”, turns module stopMST to “0”, and restarts the internal clock ICLK, and then the operationof the CPU is started from the cycle C2-8. Since the value for the CPUexecution start address RST-VEC is an address stored in the boot addressregister BAR, the operation start address of the CPU is not the bootaddress INIT-VEC, but is the address stored in the boot address registerBAR. Subsequently, in the cycle C2-8, it is updated such that the secondstandby mode signal STABY2-MODE is put to zero and the value for thestandby mode control register STBCR is put to “normal” indicative of thenormal operation mode, by which the return has been completed.

In the constitution of FIG. 33, a built-in user memory URAM is presentin the second region AE2 which does not undergo power shutdown even upontransition to the second standby mode and the data stored in thebuild-in user memory URAM is retained also in the second standby mode.Accordingly, in a case of mounting the nonvolatile FF by the minimumrequired number, the registers in the embedded circuit modules withoutretracting and returning by the non-volatile FF can be retracted andreturned by using the build-in user memory URAM. At first, the data ofthe registers are retracted by executing the program which makes itpossible to retract/return the data to/from the build-in user memoryURAM, before writing to the standby mode control register STBCR thatindicates the transition to the second standby mode. In this case, forrecovery of the register value upon returning to the normal operationmode, it needs a program of transferring the data corresponding to theaddress indicated by the boot-address register BAR, which are stored inthe built-in user memory URAM, to the register. The retracting andreturning are not necessary for the registers with no requirement ofretaining the value in the second standby mode. Accordingly, in a caseof returning from the second standby mode at a higher speed, the numberof the registers can be restricted.

FIG. 39 shows a further example of a nonvolatile FF. It has anonvolatile circuit NVC provided to the master latch in the master-slavetype latch circuit. In this constitution, data writing to thenonvolatile circuit NVC during power shutdown is conducted by using adifferential amplifier. It is different from the master-slave latchshown in FIG. 10, in additionally providing a loop comprising two stagesof inverters, precharge controlling transistor MN20, a nonvolatilecircuit NVC including an equalizer transistor MP22, writing transistors(MP20, MP21), write back transistors (MN23, MN24), writing back controltransistors (MN21, MN22), a power line for data retention VSS_SIG, awrite control signal STR to the nonvolatile circuit NVC and a datawriting back signal RSTR from the nonvolatile circuit NVC to themaster-slave type latch circuit.

The operation of the nonvolatile FF in FIG. 39 will be described withreference to FIG. 40. The normal operation is possible in a case whereboth the control signal STR and the control signal RSTR are at LO andthe virtual power line VSSM is at the ground level (0 V). In this step,in the master-slave type latch circuit, the input data D is taken intothe master latch at the rising edge of the clock CLK and is transmittedto the output Q in the subsequent stage. When the control signal STR isat LO, since the precharge controlling transistor MN20 is turned OFF andthe equalizer transistor MP22 is turned ON and, further, either thetransistor MP20 or MP21 is turned ON in accordance with the value forthe complementary node n1, /n1 of the master latch, the node nv, /nv isprecharged to the power level VDD. When the clock CLK is at LO, theslave latch retains the data to retain the output Q to the succeedingstage. The graph shows an example where the input D changes at time T1,and the input data is outputted at the rising edge at time T2. The solidline shows a case in which the input changes from LO to HI, while thebroken line shows the case where the input changes from HI to LO.

Subsequently, a sequence provided for power shut-down is conducted. Atfirst, the clock is stopped at time T3. In this case, the clock CLK isstopped at HI in order to place the master latch in a latched state.That is, this is in a phase opposite to the case of providing thenonvolatile circuit NVC to the slave latch. Then, the latched data isretracted to the nonvolatile circuit NVC at time T4. This can beconducted by turning the control signal STR2 to the level HI. When thecontrol signal STR is at the level HI, precharge is completed at timeT4′, either the transistor MP20 or MP21 in FIG. 39 turns ON and theother of them turns OFF and, in this state, the data is retracted to thelatch comprising two stages of inverters. For example, in a case wherethe input D is at HI, since the transistor MP20 turns ON and thetransistor MP21 turns OFF, the node nv is at HI while the node /nv is atLO. Subsequently, power shut-down control is conducted at time T5. Inthis case, the power on the ground side is disconnected. Further, fordecreasing the leakage current, the voltage level for the data retentioncircuit power VSS_SIG at time T6 is controlled (for example, the voltagelevel is raised to a voltage value of higher than 0 V and about 0.6 V orlower when the power VDD is at 1.2 V). This can provide an effect offurther decreasing the leakage current during the standby mode. Thewaveform shown by the broken line in the graph represents a case wherethe input data D is at LO.

Now, a description will be made regarding a sequence for returning thepower. At time T7, control of returning the level for the power line fordata retention VSS_SIG to 0 V is conducted, and control for returningthe data of the nonvolatile circuit NVC to the original master latchcorresponding to the turning of the power line for data retentionVSS_SIG to 0 V is conducted. At first, a writing preparation for thedata of the nonvolatile circuit NVC to the master latch is conducted.That is, this can be attained by turning the control signal RSTR to HIat time T8 thereby turning the writing control transistors (MN21, MN22)in FIG. 39 to ON. Since either the writing transistor (MN23 or MN24) isturned ON corresponding to the retained data in the nonvolatile circuitNVC, either one of the complementary node n1 or /n of the master latchis driven to LO to attain a returning of data.

The data writing back to the master latch is attained by driving thevirtual power line VSSM to the level LO. At time T9, control of thevirtual power line VSSM to 0 V is started, and the latch data is writtenback in accordance with the data of the nonvolatile circuit NVC. Then,correspond to the driving of the virtual power line VSSM to 0 V, thecontrol signal RSTR is put to LO at time T10 and the control signal RSTRis put to LO at time T11 thereby precharging the nonvolatile circuitNVC. Then, when the clock CLK is operated, operation is attained asusual.

Description will be made with respect to the merit of retaining dataduring power shutdown on the master latch. Generally, the size oftransistors constituting the master latch is smaller than thetransistors constituting the slave latch. Since the slave latch has todrive the load in the succeeding stage, the size of the transistorcorresponding to the load is necessary. While the circuit portion forretaining the data during power shut-down (data retaining portion) isdesirably constituted with transistors of a smaller size for decreasingthe leakage current, the size for the data retention portion also has tobe enlarged sometimes as the transistor size increases in the latch ofthe main body. Accordingly, in a case where the LSI system can transitto the standby mode by the clock CLK at HI, the size of transistors inthe data retention portion can be made smaller by providing the dataretention portion on the side of the master latch in which thetransistor size is relatively small, thereby increasing the effect ofsaving the leakage current.

Also, in a case of providing the nonvolatile circuit NVC to the slavelatch (FIG. 11 or the like), it is possible to use a differentialamplifier for the writing to the nonvolatile circuit NVC. In this case,the clock upon power shutdown may be: clock CLK=LO.

FIG. 41 shows a still further example of the nonvolatile FF, which isdifferent from the example shown in FIG. 39 in that a single controlsignal is used. Accordingly, retraction and return between thenonvolatile circuit NVC and the master latch are conductedsimultaneously. The fundamental control method is identical with thatfor FIG. 40. Description will be made with reference to FIG. 42. Whenthe control signal STR is at HI, retention data is written into thenonvolatile circuit NVC in FIG. 41 and a route to the master latch onthe side of 0 V is selectively formed in accordance with the writtendata to provide a state capable of retaining one identical data in thenonvolatile circuit NVC and the master latch. When the power is shutdown in this state, while the data in the mater latch is eliminated,since the route to the VSSM level is ensured selectively, the databefore power shut-down is returned when the virtual power line VSSM iscontrolled to 0 V in the next stage. Further, in the circuit shown inFIG. 41, when the voltage level for the power line for data retentionVSS_SIG is changed, the gate potential of the writing transistor (MN23,MN24) increases depending on the relation between the VSSM level and theVSS_SIG level to provide a concern that none of them will be turned OFFcompletely in view of the relation of the potential difference withrespect to VSSM corresponding to the source. However, also in such acase, this merely accelerates charging in the VSSM level to thedirection of the VDD level and it has an effect of decreasing leakage inthe retention circuit itself and decreasing the leakage after lapse of asufficient time. Accordingly, in the LSI application use for which nofrequent ON-OFF use is expected, an effect of reducing the powerconsumption can be obtained further by conducting the control for thepower line for data retention VSS_SIG that is conducted at time T6, T7,as shown in FIG. 40, in addition to the timing chart shown in FIG. 42.

The feature of the example shown in FIG. 41 is that the number ofcontrol signals is reduced by one. Generally, since wirings tend to becomplicated in a place where the latch is inserted, the layout can befacilitated by providing latches with a lesser number of signal lines toprovide an advantageous effect in view of the operation speed and thearea efficiency. Further, since the retraction and return of data whilethe control signal STR is at HI is interlocked with the control for thepower source shut-down, that is, control for the VSSM level, it alsoprovides an effect of facilitating the control.

The present invention concerns a semiconductor integrated circuit deviceand, more in particular, it is applied to a system LSI or amicroprocessor requiring low power consumption.

1. A semiconductor integrated circuit comprising: a first flip-flop comprising a first latch circuit and a second latch circuit; a first logic circuit connected to an output node of the first flip-flop; a first power line; a second power line; and a third power line, wherein: an output node of the first latch circuit is connected with the output node of the first flip-flop, an input node of the second latch circuit is connected with the output node of the first latch circuit or an input node of the first latch circuit, the first latch circuit and the first logic circuit is supplied with a first operation voltage through the first and the second power line, the second latch circuit is supplied with a second operation voltage through the first and the third power line, a first difference between a width of the first power line and a width of the third power line is larger than a second difference between the width of the third power line and a width of a wiring for connecting the input node of the second latch circuit and the output node or input node of the first latch circuit, a third difference between the width of the second power line and the width of the third power line is larger than the second difference, the third power line has a first state and a second state, and a potential of the third power line in the second state is higher than a potential of the third power line in the first state.
 2. The semiconductor integrated circuit device according to claim 1, wherein the potential of the third power line in the first state is the same as a potential of the second power line, and the potential of the third power line in the second state is between a potential of the first power line and the second power line.
 3. The semiconductor integrated circuit device according to claim 1, wherein the semiconductor integrated circuit device has a first mode and a second mode, the first operation voltage is supplied in the first mode, the first operation voltage is cut off and the second operation voltage is supplied in the second mode, and the third power line is controlled to be the second state when the semiconductor integrated circuit is in the second mode.
 4. The semiconductor integrated circuit device according to claim 3, further comprising: a first power supply point to supply a potential to the second power line; and a first MISFET including a source-drain path which is provided between the second power line and the first power supply line, wherein the first MISFET is controlled to an ON state in the first mode and the first MISFET is controlled to an OFF state in the second mode.
 5. The semiconductor integrated circuit device according to claim 1, wherein the first latch circuit includes a second MISFET, the second latch circuit includes a third MISFET, and an absolute value of a threshold voltage of the third MISFET is larger than an absolute value of threshold voltage of the second MISFET.
 6. The semiconductor integrated circuit device according to claim 4, wherein the first latch circuit includes a second MISFET, the second latch circuit includes a third MISFET, and an absolute value of a threshold voltage of the first MISFET is larger than an absolute value of threshold voltage of the third MISFET.
 7. The semiconductor integrated circuit device according to claim 3, further comprising: a fourth MISFET connecting the second latch circuit with the second power line, wherein the fourth MISFET is turned ON in the first mode and the fourth MISFET is turned OFF in the second mode.
 8. The semiconductor integrated circuit device according to claim 7, further comprising: a fifth MISFET connecting the second latch circuit with the third power line, wherein the fifth MISFET is turned OFF in the first mode and the fifth MISFET is turned ON in the second mode.
 9. The semiconductor integrated circuit device according to claim 3, wherein the operation voltage supplied to the second latch circuit in the second mode is lower than the operation voltage supplied to the second latch circuit in the first mode.
 10. The semiconductor integrated circuit device according to claim 1, wherein the second latch circuit includes a capacitive element.
 11. The semiconductor integrated circuit device according to claim 1, wherein the first logic circuit includes a second MISFET, the second latch circuit includes a third MISFET, and an absolute value of a threshold voltage of the third MISFET is larger than an absolute value of threshold voltage of the second MISFET.
 12. The semiconductor integrated circuit device according to claim 4, wherein the first logic circuit includes a second MISFET, the second latch circuit includes a third MISFET, and an absolute value of a threshold voltage of the first MISFET is larger than an absolute value of threshold voltage of the third MISFET. 